What is a gravatar?
A gravatar, or globally recognized avatar, is quite simply an image that follows you from site to site appearing beside your name when you do things. Avatars help identify your posts on blogs and web forums, so why not on any site?

Email: specify the e-mail used to fetch the right picture. This property is bindable.

Size: you can specify a size between 1 and 512 (pixels.) The default size of 80 pixels.

Rating: you can specify a rating of G, PG, R, or X. The default rating of G.

DefaultImage: you can specify a default image. There are "special" values that you may pass to this parameter which produce dynamic default images. These are "identicon" "monsterid" and "wavatar". If omitted it will
serve up the Gravatar default image, the blue G.